librdata - Read and write R data frames from C

Originally part of ReadStat, librdata is a small C library for reading and writing R data frames.

Features:

• Read both RData and RDS formats
• Read compressed files (requires bzip2, zlib, and lzma)
• Write factors, timestamps, logical vectors, and more

Installation

./autogen.sh
./configure
make
make install

If you're on Mac and see errors about AM_ICONV when you run ./autogen.sh, you'll need to install gettext.

Language bindings

• Python: pyreadr

Read API

Example usage:

#include"rdata.h"staticinthandle_table(constchar*name, void*ctx) {
printf("Read table: %s\n", name);
return0; /* non-zero to abort processing */
}
// Called once for all columns with the following caveats:// * `name` is NULL for some columns (see handle_column_name below)// * `data` is NULL for text columns (see handle_text_value below)staticinthandle_column(constchar*name, rdata_type_ttype,
void*data, longcount, void*ctx) {
/* Do something... */return0;
}
// Some column names appear in the file after the datastaticinthandle_column_name(constchar*name, intindex, void*ctx) {
if (debug) printf("Read column name: %s\n", name);
/* Do something... */return0;
}
// Called once per row for a text columnstaticinthandle_text_value(constchar*value, intindex, void*ctx) {
/* Do something... */return0;
}
// Called for factor variables, once for each levelstaticinthandle_value_label(constchar*value, intindex, void*ctx) {
/* Do something... */return0;
}
rdata_parser_t*parser=rdata_parser_init();
rdata_set_table_handler(parser, &handle_table);
rdata_set_column_handler(parser, &handle_column);
rdata_set_text_value_handler(parser, &handle_text_value);
rdata_set_value_label_handler(parser, &handle_value_label);
rdata_parse(parser, "/path/to/something.rdata", NULL);

See rdata.h for the full API.

Write API

Example usage:

#include"rdata.h"staticssize_twrite_data(constvoid*bytes, size_tlen, void*ctx) {
intfd=*(int*)ctx;
returnwrite(fd, bytes, len);
}
introw_count=3;
intfd=open("/path/to/somewhere.rdata", O_CREAT | O_WRONLY, 0644);
rdata_writer_t*writer=rdata_writer_init(&write_data, RDATA_WORKSPACE);
rdata_column_t*col1=rdata_add_column(writer, "column1", RDATA_TYPE_REAL);
rdata_column_t*col2=rdata_add_column(writer, "column2", RDATA_TYPE_STRING);
rdata_begin_file(writer, &fd);
rdata_begin_table(writer, "my_table");
rdata_begin_column(writer, col1, row_count);
rdata_append_real_value(writer, 0.0);
rdata_append_real_value(writer, 100.0);
rdata_append_real_value(writer, NAN);
rdata_end_column(writer, col1);
rdata_begin_column(writer, col2, row_count);
rdata_append_string_value(writer, "hello");
rdata_append_string_value(writer, "goodbye");
rdata_append_string_value(writer, NULL);
rdata_end_column(writer, col2);
rdata_end_table(writer, row_count, "My data set");
rdata_end_file(writer);
close(fd);

See rdata.h for the full API.